Final answer:
The concerns in a patient with a duodenal ulcer, acute renal failure, and a creatinine level of 6mg/dL include potential injury and loss of kidney function, as well as the need for a kidney biopsy.
Step-by-step explanation:
When a patient has a duodenal ulcer and acute renal failure with a creatinine level of 6mg/dL, there are several concerns to be aware of. One concern is the possibility of injury to the kidneys, indicated by an elevated creatinine level. Another concern is the potential loss of kidney function, which can occur in cases of persistent acute renal failure or complete loss of kidney function for more than four weeks. Additionally, it may be necessary to perform a kidney biopsy to determine the cause of the acute renal failure and assess the patient's prognosis.